The Victorians were smarter than us, study suggests

Reaction times are far from the best measure of IQ but they are important so a decline in them is certainly cause for concern -- JR

The Victorians achieved so much because they were cleverer than us, a new study suggests.

Reaction times – a reliable marker of general intelligence – have declined steadily since the Victorian era from about 183 milliseconds to 250ms in men, and from 187ms to 277ms in women.

The slowing of our reflexes points to a decrease in general intelligence equivalent to 1.23 IQ points per decade since the 1880s or about 14 IQ points overall, researchers said.

Actual IQ scores from different decades cannot be directly compared because people today enjoy better teaching, health and nutrition which would help improve their results, the scientists explained.

But the reaction times signify that the genetic component of general intelligence – which leads to the type of creativity and invention typical of the Victorian era – has been dwindling over the past century.

Dr Michael Woodley, who led the study published in the Intelligence journal this month, identified the trend by comparing reaction times from trials conducted by Victorian scientists against those carried out in recent decades.

Our declining intelligence is most likely down to a "reverse" in the process of natural selection, he explained. The most intelligent people now have fewer children on average than in previous decades, while there are higher survival rates among people with less favourable genes.

"The pressures of modern life, a nine-to-five modern lifestyle, have created all these pressures against very smart people having break-even numbers of children," he said.

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The Heretic at Heritage

Pat Buchanan

Jason Richwine, the young conservative scholar who co-authored the Heritage Foundation report on the long-term costs of the amnesty bill backed by the "Gang of Eight," is gone from Heritage.

He was purged after The Washington Post unearthed his doctoral dissertation at the JFK School of Government.

Richwine's thesis:

IQ tests fairly measure mental ability. The average IQ of immigrants is well below that of white Americans. This difference in IQ is likely to persist through several generations.

And the potential consequences of this?

"A lack of socioeconomic assimilation among low IQ immigrant groups, more underclass behavior, less social trust and an increase in the proportion of unskilled workers in the American labor market."

Richwine defended his 166-page thesis before Harvard's George Borjas, Richard Zeckhauser and Christopher Jencks, who once edited The New Republic. But while his thesis was acceptable at Harvard -- it earned Richwine a Ph.D. -- it has scandalized the Potomac priesthood.

Our elites appear unanimous: Richwine's view that intelligence is not equally distributed among ethnic and racial groups, and is partly inherited, is rankest heresy. Yet no one seems to want to prove him wrong.

Consider Richwine's contention that differences in mental ability exist and seem to persist among racial and ethnic groups.

In The Wall Street Journal last month, Warren Kozak noted that 28,000 students in America's citadel of diversity, New York City, took the eighth-grade exam to enter Stuyvesant, the Bronx School of Science and Brooklyn Tech, the city's most elite high schools. Students are admitted solely on their entrance test scores.

Of the 830 students who will be entering Stuyvesant as freshmen this fall, 1 percent are black, 3 percent are Hispanic, 21 percent are white -- and 75 percent are Asian.

Now, blacks and Hispanics far outnumber Asians in New York. But at Stuyvesant, Asians will outnumber blacks and Hispanics together 19-to-1.

Is this the result of racially biased tests at Stuyvesant?

At Berkeley, crown jewel of the California university system, Hispanics, 40 percent of California's population and an even larger share of California's young, are 12 percent of the freshman class. Asians, outnumbered almost 3-to-1 by Hispanics in California, have almost four times as many slots as Hispanics in the freshman class. Another example of racial bias?

The 2009 Programme for International Student Assessment, PISA, which measures the academic ability of 15-year-olds worldwide, found the U.S.A. falling to 17th in reading, 23rd in science, 31st in math.

Yet, Spain aside, not one Hispanic nation, from which a plurality of our immigrants come, was among the top 40 in reading, science or math.

But these folks are going to come here and make us No. 1 again?

Is there greater "underclass behavior" among Hispanics?

The crime rate among Hispanics is about three times that of white Americans, while the Asian crime rate is about a third that of whites.

Among white folks, the recent illegitimacy rate was 28 percent; among Hispanics, 53 percent. According to one study a few years back, Hispanics were 19 times as likely as whites to join gangs.

What about Richwine's point regarding "social trust"?

Six years ago, in "E Pluribus Unum: Diversity and Community in the 21st Century," Robert Putnam, author of "Bowling Alone," wrote that after 30,000 interviews he found that ethnic and racial diversity can be devastating to communities and destructive of community values.

In racially mixed communities, Putnam wrote, not only do people not trust strangers, they do not even trust their own kind.

"People living in ethnically diverse settings appear to 'hunker down,' that is, to pull in like a turtle ... (to) withdraw even from close friends, to expect the worst from their community and its leaders, to volunteer less, give less to charity and work on community projects less often, to register to vote less, to agitate for social reform more but have less faith they can actually make a difference, and to huddle unhappily in front of the television."

With the immigration bill granting amnesty to 12 million illegals, an open door to their dependents and a million new immigrants each year, almost all from the Third World, America in 2040 is going to look like Los Angeles today. Yet, it was in L.A. that Putnam found social capital at its most depleted and exhausted.

If Richwine is right, America in 2040 will be a country with whites and Asians dominating the professions, and 100 million Hispanics concentrated in semiskilled work and manual labor.

The issues Richwine raises go to the question of whether we shall survive as one nation and one people.

If our huge bloc of Hispanics, already America's largest minority at 53 million, is fed by constant new immigration, but fails for a couple of generations to reach the middle-class status that Irish, Germans, Jews, Italians and Poles attained after two generations, what becomes of our "indivisible" nation?

Rather than face this question, better to purge and silence the Harvard extremist who dared to raise it.

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The Crucifixion of Jason Richwine

Michelle Malkin presents the facts below but may not make it completely clear that there are two pieces of writing involved:  The Heritage report on the costs of immigration and Richwine's Ph.D. dissertation.  Richwine was only a junior contributor to the Heritage report. 

When the open-borders clique found that the Heritage report was too difficult to rebut, they went off on a tangent and started to shriek about Richwine's Ph.D. dissertation and the bad things he said in it.  In good Leftist "ad hominem" style, they attempted to discredit the Heritage report by saying that one of its authors was a bad man.

What they found in Richwine's dissertation did surprise me.  Richwine touched the third rail of American politics:  IQ.  IQ  studies are not terribly controversial among professors of psychology who work in the field but they are dynamite in American politics.  IQ studies are COMPLETELY inconsistent with the great Leftist myth that "All men are equal".  God may value all men equally (a rather unscriptural assertion) but they are not equal in any other sense.  All men are different.  And  IQ studies show that clearly.

Even worse, however, is that some RACES are different too.  That is not intrinsically surprising but it clashes with the widespread American wish that the whole topic of race will go away and that any effect of slavery or Jim Crow will simply wash out eventually.  It won't.  IQ tests have been showing time after time for around the last 100 years that blacks have a severe intellectual disadvantage compared to whites.  Every effort under the sun has been made to find fault with that finding but nothing works.  After all criticisms are allowed for, the large  black/white gap remains.

So why a young researcher like Richwine stepped into that quagmire, I do not know.  He showed that Hispanics too have low average IQs, though not as low as for blacks.  He was taking a huge risk of being attacked just by mentioning the topic  -- let alone by doing a comprehensive survey of the evidence on it.

I am myself a psychometrician who has made a couple of minor contributions to the academic literature on IQ but I can assure you that I said nothing on the topic until I had tenure.

So it is sad that an honest man has had his name dragged through the mud for no good reason but he really should have left the topic to those who are in a better position to resist the slings and arrows of a deeply corrupt but powerful Left.

The people I condemn most are the powers that be at Heritage.  They have fired Richwine in a cowardly attempt to take the heat off themselves.  I am a regular donor to American and Israeli conservative organizations but Heritage will get not one cent from me from now on.  Any existing donors reading this should also write to them and tell them "no more"

How low will supporters of the Gang of Eight immigration bill go to get their way? This low: They've shamelessly branded an accomplished Ivy League-trained quantitative analyst a "racist" and will stop at nothing to destroy his career as they pave their legislative path to another massive illegal alien benefits bonanza.

Jason Richwine works for the conservative Heritage Foundation. He's a Harvard University Ph.D. who co-authored a study that pegs the cost of the Ted Kennedy Memorial Open Borders Act 2.0 legislation at $6.3 trillion. Lead author Robert Rector is a senior research fellow at Heritage, a former United States Office of Personnel Management analyst and the intellectual godfather of welfare reform. He holds a master's degree in political science from Johns Hopkins University.

Both Democrats and Republicans leaped to discredit the 102-page report without bothering to read it. The Washington Post falsely claimed that the study did not take into account increased revenues from amnestied illegal alien workers. It did. Haley Barbour immediately proclaimed that the Heritage assessment of government costs incurred by amnestied illegal aliens was "not serious."

They want to talk gravitas? Let's talk gravitas. Blowhard Barbour is a career politician and paid lobbyist for the government of Mexico who has carried water for open borders since the Bush years.

Richwine received his doctorate in public policy in 2009 from Harvard University's prestigious Kennedy School of Government. He holds bachelor's degrees in mathematics and political science from American University. Before joining Heritage in 2010, he worked at the American Enterprise Institute on a dissertation fellowship.

Richwine's 166-page dissertation, "IQ and Immigration Policy," is now being used to smear him -- and, by extension, all of Heritage's scholarship -- as "racist." While the punditocracy and political establishment sanctimoniously call for "honest discussions" on race, they rush to crush bona fide, dispassionate academic inquiries into the controversial subjects of intelligence, racial and ethnic differences, and domestic policy.

Richwine's entire thesis is now online here.

Part One reviews the science of IQ. Part Two delves into empirical research comparing IQs of the native-born American population with that of immigrant groups, with the Hispanic population broken out. Richwine explores the causes of an immigrant IQ deficit that appears to persist among Hispanic immigrants to the U.S. through several generations.

The thesis analyzes social policy consequences of these findings and uses a model of the labor market "to show how immigrant IQ affects the economic surplus accruing to natives and the wage impact on low-skill natives."

The smug dismissal of Richwine's credentials and scholarship is to be expected by liberal hacks and clown operatives. But a reckless and cowardly pileup of knee-jerk dilettantes on the right -- including former McCain campaign co-chair Ana Navarro and conservative Washington Post blogger Jennifer Rubin -- have joined the character assassins of the Soros-sphere, MSNBC and Mother Jones in deeming Richwine a "racist." The drooling attack dogs of the far-left blog Daily Kos have now launched a pressure campaign against the JFK School demanding to know "why the school awarded Richwine a Ph.D. and what they plan to do in the future to prevent it from happening again.”

No researcher or academic institution is safe if this smear campaign succeeds. Richwine's dissertation committee at Harvard included George Borjas, Robert W. Scrivner Professor of Economics and Social Policy. The Cuban-born scholar received his Ph.D. in economics from Columbia. He is an award-winning labor economist, a research associate with the National Bureau of Economic Research and the author of countless books, including a widely used labor economics textbook now in its sixth edition.

Richard J. Zeckhauser, the Frank P. Ramsey Professor of Political Economy at JFK, also signed off on Richwine's dissertation. Zeckhauser earned a Ph.D. in economics from Harvard. He belongs to the Econometric Society, the American Academy of Sciences and the Institute of Medicine (National Academy of Sciences).

The final member of Richwine's "racist" thesis committee is Christopher Jencks, the Malcolm Wiener Professor of Social Policy at Harvard's JFK School. He is a renowned left-wing academic who has taught at Harvard, Northwestern, the University of Chicago and the University of California, Santa Barbara. He edited the liberal New Republic magazine in the 1960s and has written several scholarly books tackling poverty, economic inequality, affirmative action, welfare reform and, yes, racial differences ("The Black-White Test Score Gap").

The willingness of Republican Gang of 8'ers to allow a young conservative researcher and married father of two to be strung up by the p.c. lynch mob for the crime of unflinching social science research is chilling, sickening and suicidal.

These are serious people doing serious work. The crucifiers of Jason Richwine pretend to defend sound science. But if it is now inherently racist to study racial and ethnic differences among demographic groups, then it's time to shut down every social sciences department in the country.

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Debunking the IQ myth (?)

This Hampshire guff (below) was debunked months ago -- and the underlying controversy goes back about 100 years.  We have always known that IQ can be split up in various ways so the only interesting issue is how well those components correlate.  From the report below you could be forgiven for thinking that they do not correlate at all.  But they do.  The correlations were somewhat lower in the Hampshire study because of his use of a restricted (high IQ) sample, but that effect is elementary statistics and does not provide an estimate for the population as a whole.  There is NOTHING new in this study from a psychometrics viewpoint:  Just another tired old attempt to deny the facts that don't align with  the "all men are equal" myth

You may be more than a single number, according to a team of Western-led researchers. Considered a standard gauge of intelligence, an intelligence quotient (IQ) score doesn't actually provide an accurate measure of one's intellect, according to a landmark study – the largest of its kind – led by Adrian Owen of the Brain and Mind Institute at Western.

The study included more than 100,000 participants from around the globe, asking them to complete 12 cognitive tests looking at their memory, reasoning, attention and planning abilities. It found a simple IQ score is misleading when assessing one's intellectual capacity. These findings were published in an article:

"Fractioning Human Intelligence," in the journal Neuron, last month. "While there are different types of intelligence, they are all influenced by one, overarching, general intelligence. And that's what we essentially measured using something like an IQ test," said Adam Hampshire of the Brain and Mind Institute, who co-authored the paper.

Hampshire noted this kind of testing is insufficient in measuring one's intellect as it doesn't take into account multiple factors and abilities – different kinds of intelligence. "In the past, when people tried to examine how intelligence is related to the brain, they generally approached it with an assumption that there is one dominant form of intelligence which is sub-served by a specific system in the brain. What we found is that the brain regions associated with whatever the 'G Factor' is – what general intelligence is – actually housed more specialized systems, not just one," he explained.

"What we did in our study, that's been different than what's been done before, is to try and understand what the structure of intelligence is by considering the way in which the brain is organized into specialized functional systems – that is, when you look at the brain and you see there are different areas that form networks and support different types of functions," he explained.

As part of the study, researchers used functional magnetic resonance imaging (fMRI) techniques with one group of participants to show that differences in cognitive abilities correspond to individual circuits in the brain.

"There are these multiple forms of intelligence and each form is in a different brain system," Hampshire said. Results from the study found that given a broader range of cognitive tasks, the differences in ability relate to at least three components of intelligence – short-term memory, reasoning and verbal aptitude.

These three components combined create an intelligence, or "cognitive profile." In other words, there is no single measure of intelligence.

Given the range of participants in the study, results also gave researchers new insight into how factors such as age, gender and the tendency to play computer games can influence brain function. While age had a profound negative effect on memory and reasoning abilities, playing computer games helped certain individuals perform better on tests assessing reasoning and short-term memory.

"My hope is that this (study) pens the debate back up on how we should conceive of and measure human intelligence. We very often hear these comparisons (of intelligence) and it's a terrible oversimplification. People should be skeptical when they hear these reports of population differences in IQ; it shouldn't be a unitary measure. Examining the social demographic correlations in more detail will help to understand them better. The patterns need to be examined with a more detailed model," Hampshire noted.

"We've identified different forms of intelligence now which relate to different systems in the brain. And we've also researched some into correlations with types of intelligence and different social demographics variables. What's next is refining that model of intelligence."

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IQ tests are 'meaningless and too simplistic' claim researchers

This appears to have been based on an internet survey and such surveys  are notorious for giving non-representative results.  A large sample size is no substitute for representativeness

The underlying controversy, however, is as old as the hills:  Should IQ be measured as a set of subscores or as one overall score?  Among psychometricians it is known as the Spearman/Thurstone controversy and dates back to the beginning of the last century.

The accepted answer is to present results both ways:  As one overall score plus a set of sub-scores.  Results can reasonably be represented both ways because the subscores are correlated.  Knowing a person's subscore on (say) verbal ability will give you a useful (but not of course perfect) prediction of his mathematical ability.  That has repeatedly been demonstrated.

The novelty in the report below is that the various sub-abilities were said to be NOT correlated  -- which runs contrary to 100 years of findings by others.  I note however that the authors are more cautious in the underlying journal article.  They say:  

Using simulations based on neuroimaging data, we show that the higher-order factor “g” is accounted for by cognitive tasks corecruiting multiple networks. Finally, we confirm the independence of these components of intelligence by dissociating them using questionnaire variables. We propose that intelligence is an emergent property of anatomically distinct cognitive systems, each of which has its own capacity.

That sounds to me as if they admit the existence of a general factor but find that the subfactors don't all use exactly  the same parts of the brain -- which should be no surprise to anyone. 

There is also a question about how comprehensive were the test items used.  Without seeing all the questions, I get the impression  that a deliberate attempt was made to find questions that would not produce correlated results.  One can ask plenty of questions not conceptually related to intelligence and in that case intercorrelations are not be be expected.  In psychometrican's terms, the test would lack construct validity.

The journal article is "Fractionating Human Intelligence" by Hampshire et al.  I look forward to seeing a more detailed examination of the article by those who specialize in IQ studies

After conducting the largest ever study of intelligence, researchers have found that far from indicating how clever you are, IQ testing is actually rather ‘meaningless’.

In a bid to investigate the value of IQ, scientists asked more than 100,000 participants to complete 12 tests that required planning, reasoning, memory and attention.  They also filled in a survey on their background.

They discovered that far from being down to one single factor, what is commonly regarded as intelligence is influenced by three different elements - short-term memory, reasoning, and verbal ability.  But being good at one of these factors does not mean you are going to be equally gifted at the other two.

Scientists from Canada’s Western University in Ontario, also scanned some of the participants’ brains while they undertook the tests.

They found that different parts of the brain were activated when they were tested on each of the three factors.

Traditional IQ tests are ‘too simplistic’, according to the research, which found that what makes someone intelligent is too complex to boil down to a single exam.

IQ, which stands for Intelligence Quotient, is an attempt to measure how smart an individual is.  The average IQ is 100. Mensa, the high IQ society, only accepts individuals who score more than 148, putting them in the top two per cent of the population.

The new study, published in the journal Neuron, suggests that intelligence is too complex to be represented by a single number.

Study leader Dr Adrian Owen, a British neuroscientists based at Western University in Canada, said an ‘astonishing’ number of people had contributed to the research.

‘We expected a few hundred responses, but thousands and thousands of people took part, including people of all ages, cultures and creeds and from every corner of the world,’ he said.

‘When you take 100,000 people and tested their brain function, we couldn’t find any evidence for a single uniform concept of intelligence.

‘The best we could manage is get it down to three elements that contribute to intelligence. But they are completely different factors, unrelated to one another, and you could be brilliant at one and awful at another.  For example, the absent-minded professor.

‘IQ tests are pretty meaningless - if you are not good at them, all it proves is that you are not good at IQ tests.

'It does not say anything about your general intelligence.’ The majority of IQ tests were developed in the 50s and 60s when the way we thought and interacted with the world was different, said Dr Owen.

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Jensen and Flynn

Thomas Sowell

Anyone who has followed the decades-long controversies over the role of genes in IQ scores will recognize the names of the two leading advocates of opposite conclusions on that subject-- Professor Arthur R. Jensen of the University of California at Berkeley and Professor James R. Flynn, an American expatriate at the University of Otago in New Zealand.

What is so unusual in the academic world of today is that Professor Flynn's latest book, "Are We Getting Smarter?" is dedicated to Arthur Jensen, whose integrity he praises, even as he opposes his conclusions. That is what scholarship and science are supposed to be like, but so seldom are.

Professor Jensen, who died recently, is best known for reopening the age-old controversy about heredity versus environment with his 1969 article titled, "How Much Can We Boost IQ and Scholastic Achievement?"

His answer-- long since lost in the storms of controversy that followed-- was that scholastic achievement could be much improved by different teaching methods, but that these different teaching methods were not likely to change I.Q. scores much.

Jensen argued for educational reforms, saying that "scholastic performance-- the acquisition of the basic skills-- can be boosted much more, at least in the early years, than can the IQ" and that, among "the disadvantaged," there are "high school students who have failed to learn basic skills which they could easily have learned many years earlier" if taught in different ways.

But, regardless of what Arthur Jensen actually said, too many in the media, and even in academia, heard what they wanted to hear. He was lumped in with earlier writers who had promoted racial inferiority doctrines that depicted some races as being unable to rise above the level of "hewers of wood and drawers of water."

These earlier writers from the Progressive era were saying, in effect, that there was a ceiling to the mental potential of some races, while Jensen argued that there was no ceiling but, by his reading of the evidence, a difference in average IQ, influenced by genes.

When I first read Arthur Jensen's landmark article, back in 1969, I was struck by his careful and painstaking analysis of a wide range of complex data. It impressed me but did not convince me. What it did was cause me to dig up more data on my own.

A few years later, I headed a research project that, among other things, collected tens of thousands of past and present IQ scores from a wide range of racial and ethnic groups at schools across the United States. Despite serious limitations in these data, due to constraints of time and circumstances, these data nevertheless threw some additional light on the subject.

A feature article of mine in the Sunday New York Times Magazine of March 27, 1977 pointed out that any number of white groups, here and overseas, had at some point in time had IQs similar to, and in some cases lower than, the IQs of black Americans. During the First World War, for example, white soldiers from some Southern states scored lower on army mental tests than black soldiers from some Northern states.

Professor Jensen read this article and came over to Stanford University to meet with me and discuss the data. That is what a scholar should do when challenged. But the opposite approach was shown by Professor Kenneth B. Clark, who earlier had sought to dissuade me from doing IQ research. He said it would "dignify" Jensen's work, which Clark wanted ignored or discredited instead.

Unfortunately, Professor Clark's ideological approach became far more common in academia, so much so that Jensen's attempts to speak on campuses around the country provoked dangerous disruptions, instead of reasoned arguments.

Years later, Professor James R. Flynn created the biggest challenge to the hereditary theory of intelligence, when he showed that whole nations had risen to much higher results on IQ tests in just one or two generations. Genes don't change that fast.

Professor Flynn told me that he would never have done his research, except that it was provoked by Jensen's research. That is just one of the reasons for having a free marketplace of ideas, instead of turning academic campuses into fortresses of politically correct intolerance.

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Sowell's comments are those of an unusually decent man but his argument is unpersuasive.  You can to this day find some whites who are dumber than some blacks but it is the groups OVERALL (and preferably across time) that are of greatest interest and the overall black/white gap has been consistent as far back as it has been measured.  But there are exceptions to every rule and some blacks are very bright.  Sowell is one of them.

High IQ as just one part of biological good functioning

I have for some years been putting forward evidence in favor of the view that high IQ is just one aspect of general biological good functioning.  I never thought to get the NYT on my side but you can read it below

FEW of us are as smart as we'd like to be. You're sharper than Jim (maybe) but dull next to Jane. Human intelligence varies - and this matters because smarter people generally earn more money, enjoy better health, raise smarter children, feel happier and, just to rub it in, live longer as well.

But where does intelligence come from? How is it built? Researchers have tried hard to find the answer in our genes. With the rise of inexpensive genome sequencing, they've analysed the genomes of thousands of people, looking for gene variants that clearly affect intelligence, and have found a grand total of two.

One determines the risk of Alzheimer's disease and affects IQ only late in life; the other seems to build a bigger brain, but on average it raises IQ by all of 1.29 points.

Other genetic factors may be at work. A report last year concluded that several hundred gene variants taken together seemed to account for 40 per cent to 50 per cent of the differences in intelligence among the 3500 subjects in the study.

But the authors couldn't tell which of these genes created any significant effect. When they tried to use the genes to predict differences in intelligence, they could account for only 1 per cent of the differences in IQ.

"If it's this hard to find an effect of just 1 per cent," Robert Plomin, a professor of behavioural genetics at King's College London, told New Scientist, "what you're really showing is that the cup is 99 per cent empty."

But is the genetic cup really empty, or are we just looking for the wrong stuff?

A developmental neurogeneticist Kevin Mitchell at Trinity College Dublin, thinks the latter. In an essay he published in July on his blog, Wiring the Brain, Mitchell proposed that instead of thinking about the genetics of intelligence, we should be trying to parse "the genetics of stupidity," as his title put it. We should look not for genetic dynamics that build intelligence, but for those that erode it.

The premise for this argument is that once natural selection generated the set of genes that build our big, smart human brains, those genes became "fixed" in the human population; virtually everyone receives the same set and precious few variants affect intelligence. This could account for the researchers' failure to find many variants of measurable effect.

But in some other genetic realms we do differ widely, for example, mutational load - the number of mutations we carry. This tends to run in families, which means some of us generate and retain more mutations than others do. Among our 23,000 genes, you may carry 500 mutations while I carry 1000.

Most mutations have no effect. But those that do are more likely to bring harm than good, Mitchell says , because "there are simply many more ways of screwing something up than of improving it".

Open the hood of a smooth-running car and randomly turn a few screws, and you'll almost certainly make the engine run worse than before. Likewise, mutations that change the brain's normal development or operation will probably slow it down. Smart Jane may be less a custom-built, high-performance model than a standard version pulling a smaller mutational load.

We also inherit - through genes yet to be identified, of course - a trait known as developmental stability. This is essentially the accuracy with which the genetic blueprint is built.

Developmental stability keeps the project on track. It reveals itself most obviously in physical symmetry. The two sides of our bodies and brains are constructed separately but from the same blueprint of 23,000 genes. If you have high developmental stability, you'll turn out highly symmetrical. Your feet will be the same shoe size, and the two sides of your face will be identical.

If you're less developmentally stable, you'll have feet up to a half size different and a face that's like two faces fused together. Doubt me? Take a digital image of your face and split it down the middle. Then make a mirror image copy of each half and attach it to its original. In the two faces you've just made - one your mirrored left side, the other your right - you'll behold your own developmental stability, or lack thereof.

Both those faces might be better looking than you are, for we generally find symmetrical faces more attractive. It also happens that symmetry and intelligence tend to run together, because both run with developmental stability. We may find symmetrical faces attractive because they imply the steadiness of genetic development, which creates valuable assets for choosing a mate, like better general fitness and, of course, intelligence - or as Mitchell might put it, a relative lack of stupidity.

These ideas don't strike geneticists as radical or contrary. A geneticist at Princeton University Leonid Kruglyak, who studies yeast and flatworms, noted that geneticists had long recognised that mutations could "throw sand in the gears of the brain" and that complex traits arose in complicated ways.

"Talking about 'a gene for a trait' is a shorthand at best," he wrote, "and a well-known fallacy at worst."

Mitchell agreed. "This isn't a brand new idea," he says. "But it's not one that has been generally adhered to in intelligence studies."

Not brand new, perhaps, but it's this kind of "inversion of thought" that can spark new approaches to intractable problems.

Dr Jay Giedd, who studies brain development at the US National Institutes of Health, has done research suggesting that the brain blooms through many small arcs of development that make it responsive to experience - and vulnerable to error. At first, he says, he was sceptical of Mitchell's idea. Then he discussed it with colleagues at a neuroscience meeting.

"My initial thought was that it would be easy to sink the argument," Giedd says. But the more they discussed it, the more sense it made. "Everybody I ran it by seemed to feel the logic is sound."

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